As for a direct injection engine, it is required to increase an injection pressure of fuel and to atomize the injected fuel in order to ensure its combustibility. A feed pump pumps up fuel from a fuel tank and a high-pressure pump pressurizes the fuel. The pressurized fuel is introduced into a fuel injector through a delivery pipe. A fuel pressure sensor is provided in a delivery pipe to detect the pressurized fuel pressure. The feed pump and the high-pressure pump are controlled so that the fuel pressure agrees with a target fuel pressure.
Such a high-pressure fuel supply system has a diagnosis function and a fail-safe function. For example, JP-11-210532A shows a system in which the pressurizing function of the high-pressure pump is suspended and the fuel pressure is decreased to a feed pressure depending on the feed pump when a malfunction is detected in a fuel pressure sensor. The engine runs while receiving the fuel from the feed pump. JP-2008-175080A shows a system in which the fuel pressure is ensured by a feed pump when a malfunction is detected in a high-pressure pump. The engine runs while receiving the fuel from the feed pump.
As above, in the high-pressure fuel supply system shown in JP-11-210532A and JP-2008-175080A, when a malfunction is detected in a fuel pressure sensor or a high-pressure pump, a fail-safe control is executed in order that the engine runs as long as possible while receiving the fuel from a feed pump.
When a malfunction is detected in a fuel pressure sensor or a high-pressure sensor, it is preferable that an appropriate fail-safe control is executed according to a portion/part in which a malfunction occurs and a time point at which a malfunction occurs. However, in the above described conventional system, it is not distinguished between a malfunction in a fuel pressure sensor and a malfunction in a high-pressure pump. When a malfunction occurs in a system, a predetermined fail-safe control is executed without respect to a faulty portion and a time point at which the malfunction occurs.